This application is based on Application No. 2001-366369, filed in Japan on Nov. 30, 2001, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates in general to an excitation controller for a synchronous machine. More particularly, the invention relates to an excitation controller for a synchronous machine which contributes to the enhancement of stabilizing a voltage in an electric power system.
2. Description of the Related Art
A conventional excitation controller for a synchronous machine described in U.S. Pat. No. 6,265,852 B1 has a high side voltage control (hereinafter, referred to as xe2x80x9cHSVCxe2x80x9d for short, when applicable) function of controlling a high side voltage of a main transformer in such a way that it becomes equal to a control reference value. This HSVC function is a function which is added to an automatic voltage regulator (hereinafter, referred to as xe2x80x9cAVRxe2x80x9d for short, when applicable) in the form of software.
Therefore, when it is intended that the HSVC function is added to existing control equipment, there arises the problem that since it is necessary to replace the overall AVR with a desired one, this results in an increase in cost.
In the light of the foregoing, the present invention has been made in order to solve the above-mentioned problem associated with the prior art, and it is therefore an object of the present invention to obtain an excitation controller for a synchronous machine in which the HSVC function can be obtained without exchanging an existing AVR.
An excitation controller for a synchronous machine according to the present invention includes: a voltage detector for detecting an output terminal voltage of the synchronous machine connected to a transmission system through a transformer; a current detector for detecting a current outputted by the synchronous machine; a module type HSVC (High Side Voltage Control) apparatus for operating arithmetically a reactive power on the basis of output signals from the voltage detector and the current detector, operating arithmetically a reactive current value from the generator terminal voltage and the reactive power, operating arithmetically a high side voltage value from the reactive current value thus arithmetically operated and a reactance of the transformer and outputting a correction signal based on a deviation between the high side voltage value thus arithmetically operated and a voltage setting value; an automatic voltage regulator, having a voltage setter, for outputting a command which is obtained by adding the correction signal to a voltage setting value provided by the voltage setter; and an exciter for carrying out field control of said synchronous machine on the basis of the command issued from the automatic voltage regulator.
Also, the module type HSVC apparatus includes an HMI (Human Machine Interface) for carrying out setting of a reference voltage, and setting and display of control logic.
Also, the module type HSVC apparatus includes a connection unit having a communication function for connecting the HMI to a network.
Also, the module type HSVC apparatus has an input unit for inputting therethrough a voltage setting value from the automatic voltage regulator and outputs a correction signal based on a deviation between the inputted voltage setting value and the arithmetically operated high side voltage value.
Also, the synchronous machines are connected in parallel with one another to the transmission system through the transformer, the voltage detector, the current detector, the module type HSVC apparatus, the automatic voltage regulator, and the exciter are provided for each of the synchronous machines, and each of the module type HSVC apparatuses carries out control for suppressing a cross current on the basis of an input of a reactive power from the other module type HSVC apparatus.
Further, the module type HSVC apparatus includes an analog output unit for outputting therethrough an arithmetic operation result.